lib/gethrxtime.c

   1 /* gethrxtime -- get high resolution real time
   2
   3    Copyright (C) 2005-2007, 2009-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 #include <config.h>
  21
  22 #define GETHRXTIME_INLINE _GL_EXTERN_INLINE
  23 #include "gethrxtime.h"
  24
  25 #if ! (HAVE_ARITHMETIC_HRTIME_T && HAVE_DECL_GETHRTIME)
  26
  27 #include <sys/time.h>
  28 #include "timespec.h"
  29
  30 /* Get the current time, as a count of the number of nanoseconds since
  31    an arbitrary epoch (e.g., the system boot time).  Prefer a
  32    high-resolution clock that is not subject to resetting or
  33    drifting.  */
  34
  35 xtime_t
  36 gethrxtime (void)
  37 {
  38 # if HAVE_NANOUPTIME
  39   {
  40     struct timespec ts;
  41     nanouptime (&ts);
  42     return xtime_make (ts.tv_sec, ts.tv_nsec);
  43   }
  44 # else
  45
  46 #  if defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME
  47   {
  48     struct timespec ts;
  49     if (clock_gettime (CLOCK_MONOTONIC, &ts) == 0)
  50       return xtime_make (ts.tv_sec, ts.tv_nsec);
  51   }
  52 #  endif
  53
  54 #  if HAVE_MICROUPTIME
  55   {
  56     struct timeval tv;
  57     microuptime (&tv);
  58     return xtime_make (tv.tv_sec, 1000 * tv.tv_usec);
  59   }
  60
  61 #  else
  62   /* No monotonically increasing clocks are available; fall back on a
  63      clock that might jump backwards, since it's the best we can do.  */
  64   {
  65     struct timespec ts;
  66     gettime (&ts);
  67     return xtime_make (ts.tv_sec, ts.tv_nsec);
  68   }
  69 #  endif
  70 # endif
  71 }
  72
  73 #endif